1. Field of the Invention
The present invention relates to a Liquid-Crystal Display (LCD) device and more particularly, to an LCD device of the active-matrix addressing type that are capable of simultaneously displaying a television (TV) image and a car navigation image on the same screen at unequal resolutions, and a driving method of the device.
2. Description of the Prior Art
In general, on-vehicle LCD devices are used for displaying a car navigation image or a TV image. The vertical resolution of the on-vehicle LCD devices is typically set as approximately 240 scanning lines, which is optimum for displaying TV images.
FIG. 1 schematically shows the configuration of a prior-art LCD module as an example of LCD devices of this sort.
The prior-art LCD module of FIG. 1 comprises an LCD panel 310, two horizontal drivers 301 and 302 serving as data drivers, and a vertical driver 305 serving as a scanning driver.
The LCD panel 310 has scanning lines 311 extending along the rows of a matrix and arranged along the columns thereof at equal intervals, and data lines 312 extending along the columns of the matrix and arranged along the rows thereof at equal intervals. The panel 310 further has display elements (not shown) located at the respective intersections P of the scanning and data lines 311 and 312. The display elements constitute the respective pixels of the LCD device and therefore, these pixels are arranged in the matrix array. Each of the pixels arranged along any one of the data lines 312 corresponds to each of the rows of the matrix. Each of the pixels corresponding to the rows of the matrix is selected by scanning signals supplied through the scanning lines 311 and are driven by data signals supplied through the data lines 312.
The horizontal driver 301 receives a horizontal start signal HST, a horizontally-shifting clock signal HCK, and a video data signal VD. The driver 301 drives the pixels located on the left-hand side with respect to the panel 310 in FIG. 1.
The horizontal driver 302 receives the video data signal VD. Also, the driver 302 receives a horizontal start signal HSTxe2x80x2 and a horizontally-shifting clock signal HCKxe2x80x2 supplied from the driver 301. The signal HSTxe2x80x2 has a specific temporal delay with respect to the horizontal start signal HST. Similarly, the signal HCKxe2x80x2 has a specific temporal delay with respect to the horizontally-shifting clock signal HCK. The driver 302 drives the pixels located on the right-hand side with respect to the panel 310 in FIG. 1.
The vertical driver 305 receives a vertical start signal VST and a vertically-shifting clock signal VCK.
The panel 310 is driven by the horizontal drivers 301 and 302, which is due to the fact that the total number of the data lines 312 is greater than the output terminals of each of the drivers 301 and 302.
In recent years, there has been a tendency that the amount of information contained in the navigation images increases according to the ongoing functional expansion of car navigation systems. Under such tendency, there has been the growing need to enlarge the screen size and to raise the resolution in the on-vehicle LCD devices. Furthermore, there has been the need to make it possible to display different images on the two horizontally-divided display areas of the screen, which is termed the xe2x80x9cdual-image displaying functionxe2x80x9d.
It is comparatively easy to display two different images on the horizontally-divided display areas of the screen at an equal vertical resolution. For example, it can be realized by applying different video data VD to the horizontal drivers 301 and 302 in the module of FIG. 1.
However, it is not easy to display two different images on the horizontally-divided display areas of the screen at unequal vertical resolutions. For example, it is not easy to display a high-resolution navigation image and a normal-resolution TV image on the divided display areas. This is because the displayable resolution is determined by a lower one of the resolutions. As a result, there arises a problem that the resolution of the navigation image is degraded.
On the other hand, to realize high-quality images, there has been known a technique that an interlace signal is converted to a non-interlace signal by double-scanning conversion and then, the non-interlace signal thus produced is used for displaying high-quality images. This is termed the xe2x80x9cdouble-scanning techniquexe2x80x9d. If this technique is used, the vertical resolution can be improved.
A prior-art LCD device of this sort is disclosed in the Japanese Non-Examined Patent Publication No. 5-64108 published in December 1993. The LCD panel of this prior-art device is comprised of an odd-numbered row data driver for driving the pixels in the odd-numbered rows of the matrix, an odd-numbered row scanning driver for scanning the same pixels, an even-numbered row data driver for driving the pixels in the even-numbered rows of the matrix, and an odd-numbered row scanning driver for scanning the same pixels. These four drivers are operable independently. Each of the odd- and even-numbered row data drivers receives alternately an actual signal generated by a double-scanning converter circuit and an interpolating signal at each vertical scanning period (1V). Each of the odd- and even-numbered row scanning drivers drives simultaneously the pixels in the odd-numbered or even-numbered rows.
Thus, the prior-art LCD device disclosed in the Publication No. 5-64108 provides high-quality TV images without raising the operating frequency of the data and scanning drivers.
Another prior-art LCD device of this sort is disclosed in the Japanese Non-Examined Patent Publication No. 10-62811 published in March 1998. The LCD panel of this device is comprised of a first plurality of scanning lines and a second plurality of scanning lines, and a first plurality of data lines and a second plurality of data lines. The first plurality of scanning lines are driven by a scanning driver and the second plurality of scanning lines are driven by another scanning driver. The first plurality of data lines are connected to the pixels in the odd-numbered rows of a matrix. The second plurality of data lines are connected to the pixels in the even-numbered rows of the same matrix. The first plurality of scanning lines receive writing or resetting pulses. The second plurality of scanning lines receive writing or resetting pulses. The first and second pluralities of scanning lines are simultaneously driven by their corresponding scanning drivers. The pixels in the odd-numbered rows receive one of the writing and resetting pulses and at the same time, those in the even-numbered rows of the same matrix receive the other.
Thus, the prior-art LCD device disclosed in the Publication No. 10-62811 improves the contrast while the driving voltage is kept low, thereby providing high-quality images.
However, the prior-art LCD devices disclosed in the Publication Nos. 5-64108 and 10-62811 were developed in order to improve the quality of image displayed as a single image on the screen. As a result, similar to the prior-art LCD module shown in FIG. 1, it is difficult for these prior-art LCD devices to display two different images on the horizontally-divided display areas of the screen at unequal vertical resolutions.
Accordingly, an object of the present invention is to provide an LCD device and its driving method that make it possible to simultaneously display two images on a screen at unequal resolutions.
Another object of the present invention is to provide an LCD device and its driving method that make it possible to simultaneously display a high-resolution car navigation image and a normal-resolution TV image on a screen.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
According to a first aspect of the present invention, an LCD device is provided, which is comprised of:
(a) an LCD panel having pixels arranged in a matrix array with rows and columns;
the panel having a first display area and a second display area;
part of the pixels being located in the first display area and the remainder of the pixels being located in the second display area;
(b) a first horizontal driver for supplying a first data to the pixels arranged along the odd-numbered rows of the matrix in the first display area;
(c) a second horizontal driver for supplying a second data to the pixels arranged along the odd-numbered rows of the matrix in the second display area;
(d) a third horizontal driver for supplying a third data to the pixels arranged along the even-numbered rows of the matrix in the first display area;
(e) a fourth horizontal driver for supplying a fourth data to the pixels arranged along the even-numbered rows of the matrix in the second display area;
(f) a first vertical driver for selecting the pixels arranged along the odd-numbered rows of the matrix in the first and second display areas; and
(g) a second vertical driver for selecting the pixels arranged along the even-numbered rows of the matrix in the first and second display areas.
The first and third horizontal drivers simultaneously supply the first and third data to the pixels arranged along one of the odd-numbered rows of the matrix in the first display area and those arranged along an adjoining one of the even-numbered rows of the matrix to the supplied row in the first display area, respectively.
With the LCD device according to the first aspect of the present invention, the first and second horizontal drivers are provided to supply the first and second data to the pixels arranged along the odd-numbered rows of the matrix in the first and second display areas of the LCD panel, and the third and fourth horizontal drivers are provided to supply the third and fourth data to the pixels arranged along the even-numbered rows of the matrix in the first and second display areas of the panel. The first vertical driver is provided to select the pixels arranged along the odd-numbered rows in the first and second display areas. The second vertical driver is provided to select the pixels arranged along the even-numbered rows in the first and second display areas.
Moreover, the first and third horizontal drivers simultaneously supply the first and third data to the pixels arranged along one of the odd-numbered rows in the first display area and those arranged along an adjoining one of the even-numbered rows to the row supplied with the first data in the first display area, respectively.
Thus, when the first and third data have the same content, an image is displayed at a relatively low resolution in the first display area. When the first and third data have different contents, an image is displayed at a relatively high resolution in the first display area. As a result, two images with different resolutions can be simultaneously displayed in the first and second display areas. This means that two images can be displayed on the screen at unequal resolutions.
If one of the two images is car navigation image and the other is TV image, a high-resolution car navigation image and a normal-resolution TV image can be displayed simultaneously on the screen.
In a preferred embodiment of the device according to the first aspect of the invention, the first vertical driver selects the pixels arranged along one of the odd-numbered rows in the first display area and at the same time, the second vertical driver selects the pixels arranged along an adjoining one of the even-numbered rows to the row selected by the first vertical driver in the first display area.
In another preferred embodiment of the device according to the first aspect of the invention, the first and third horizontal drivers are formed on a first horizontal driver IC and the second and fourth horizontal drivers are formed on a second horizontal driver IC. In this embodiment, there is an additional advantage that electrical wiring or interconnection on the panel is facilitated, and that the fabrication cost of the LCD device itself is lowered.
According to a second aspect of the present invention, a driving method of an LCD device is provided, which is comprised of the steps of:
(a) preparing an LCD panel having pixels arranged in a matrix array with rows and columns;
the panel having a first display area and a second display area;
part of the pixels being located in the first display area and the remainder of the pixels being located in the second display area;
(b) supplying a first data to the pixels arranged along the odd-numbered rows of the matrix in the first display area;
(c) supplying a second data to the pixels arranged along the odd-numbered rows of the matrix in the second display area;
(d) supplying a third data to the pixels arranged along the even-numbered rows of the matrix in the first display area;
(e) supplying a fourth data to the pixels arranged along the even-numbered rows of the matrix in the second display area;
(f) selecting the pixels arranged along the odd-numbered rows of the matrix in the first and second display areas; and
(g) selecting the pixels arranged along the even-numbered rows of the matrix in the first and second display areas.
The first and third data are simultaneously supplied to the pixels arranged along one of the odd-numbered rows of the matrix in the first display area and to those arranged along an adjoining one of the even-numbered rows of the matrix to the supplied row in the first display area, respectively.
With the driving method of an LCD device according to the second aspect of the present invention, because of substantially the same reason as described about the LCD device according to the first aspect, two images with different resolutions can be simultaneously displayed in the first and second display areas. This means that two images can be displayed on the screen at unequal resolutions. If one of the two images is car navigation image and the other is TV image, a high-resolution car navigation image and a normal-resolution TV image can be displayed simultaneously on the screen.
In a preferred embodiment of the method according to the second aspect of the invention, the pixels arranged along one of the odd-numbered rows in the first display area are selected and at the same time, the pixels arranged along an adjoining one of the even-numbered rows to the row selected in the first display area are selected.